In general, an exhaust gas recirculation (EGR) system is a system for reducing nitrogen oxide (NOx) emissions by recirculating a portion of exhaust gas of an engine back to the engine cylinders such that a temperature of a combustion chamber is lowered due to the increase of CO2 concentration of the intake air. The EGR system includes an exhaust gas heat exchanger, namely an EGR cooler, cooling exhaust gas using coolant. The EGR cooler cools hot exhaust gas at a temperature of about 700° C. down to a temperature of 150° C.˜200° C.
FIG. 1 is a perspective view illustrating a conventional EGR cooler; and FIG. 2 is an exploded perspective view illustrating the conventional EGR cooler. As shown in FIGS. 1 and 2, the conventional EGR cooler, which is formed by assembly of an upper shell piece and a lower shell piece, includes: body shells 1 and 2, opposite ends of which are open; a laminated tube core fixedly disposed inside the body shells 1 and 2 and formed by laminating a plurality of gas channels 8 side by side by brazing the gas channels; burred plates 3 provided with a plurality of holes, into which each of the plurality of gas channels 8 is inserted, so as to support opposite ends of the laminated tube core; a pair of end tanks 4 covering end portions of the plurality of gas channels 8, wherein each is provided with an exhaust passage, a cross-sectional area of which is gradually reduced as approaching an end of the associated end tank defining an exhaust gas inlet or an exhaust gas outlet; and flanges 5 fittingly inserted into end portions of the end tanks 4 to be coupled to the end tanks 4. The pair of end tanks 4 is each configured to be coupled to the laminated tube core so as to cover an associated end of the laminated tube core, and thereby at the exhaust gas inlet, the exhaust gas is induced toward an inlet of each of the plurality of gas channels 8 and at the exhaust gas outlet, the exhaust gas via the plurality of gas channels 8 is combined and discharged. Further, the body shells 1 and 2 of the EGR cooler are coupled to a pair of coolant pipes 7 to allow a coolant to flow in and out. The coolant flows inside the body shells 1 and 2 while contacting with outer surfaces of the plurality of gas channels 8, and thereby cooling the exhaust gas flowing through the plurality of gas channels 8.
However, the conventional EGR cooler is disadvantageous in that as the end tanks 4 and the burred plates 3 are required to be separately assembled with the opposite ends of the gas channels 8 from the body shell, a large number of components are required, the assembly thereof is difficult, and thus manufacturing cost is high.